Anatomy of the CVS Flashcards
Where is the heart located?
Middle mediastinum (area between the pleural cavities)
At what vertebral level is the top of the middle mediastinum?
Between T4 and T5
What main type of tissue does not have a blood supply?
Cartilage
What tissues/organs do not receive lymphatic drainage?
Brain + spinal cord
Eyes
Bone marrow
(cartilage?)
What are the 2 main circulations of the CVS?
Pulmonary
Systemic
What 2 other ‘circulations’ are present in the body that are associated with the CVS?
Hepatic portal circulation
Lymphatic circulation
What is the hepatic portal circulation?
Circulation that links the digestive tract directly to the liver (“hepatic”) before continuing to the heart
Describe each of the following for the pulmonary artery:
- origin
- main parts
- relevant anatomical positions
Pulmonary trunk leaves Right ventricle
Trunk splits shortly after, into the left and right pulmonary arteries
Right pulmonary artery passes under aortic arch and behind the superior vena cava
Left pulmonary artery ends up passing behind the pulmonary vein (but this is not that close to the heart)
Describe each of the following for the aorta:
- origin
- main parts
- relevant anatomical positions
Ascending Aorta leaves the left ventricle
Aortic arch - the vessel arches over the right pulmonary artery and continues downwards as the descending aorta
3 arteries leave the Aortic arch at its peak:
- Bracheocephalic artery
- Common Carotid artery
- Left Subclavian artery
What does the bracheocephalic artery continue to form?
Right subclavian & Right common carotid arteries
What is visible when looking at the heart anteriorly?
in the way it sits in the body
Right atrium & ventricle
Left ventricle
What chamber is the base of the heart?
Left atrium
Why does apex mean something different for the heart, than it does for the lungs?
The apex of the heart is at the bottom
Apex of the lungs are at the top
What blood vessels run parallel with the vertebral column?
in the abdominal area
Vena Cava
Descending aorta
Azygos vein
In the recumbent position, the heart lies between what vertebral levels?
T5-T8
Describe the surface anatomy position of the apex of the heart
Left ventricle - 5th left intercostal space in the midclavicular line
Where is the Base of the heart located?
In front of the oesophagus
Moves up and down with breaths
How does the position of the heart different in children?
Higher up and lies more horizontal
What is situs inversus?
congenital condition in which the major visceral organs are reversed or mirrored from their normal positions. The normal arrangement of internal organs is known as situs solitus
What is Situs inversus’s effect on the heart?
Dextrocardia
What lies anteriorly to the heart
Sternum and costal cartilages 4-7
Anterior edges of the lungs and pleurae
Thymic remnants
Sternal angle in line with the aortic arch
What lies posteriorly to the heart?
Oesophagus
Descending aorta
Thoracic vertebrae
What lies laterally to the heart?
Lungs
Phrenic nerve
What lies inferiorly to the heart?
Central tendon of the diaphragm
Describe the different layers of the heart
Endocardium (innermost):
- Epithelium
- Basement memb
- Connective tissue
Myocardium - muscle
Epicardium (outermost):
- CT
- BM
- Visceral pericardium (epicardium epithelium)
How is the serous pericardium similar to the pleura?
Double layered, with (pericardial) in the middle
Inner layer is the epithelial layer of the epicardium (visceral layer of the serous pericardium)
Outer layer is the Parietal layer of the pericardium
What encloses the parietal layer of the serous pericardium?
Fibrous pericardium
Which layer of the heart wall is thinnest and which is thickest?
Endocardium is the thinnest
Myocardium is thickest
Describe the structure of the endocardium
Simple squamous epithelium sitting on basement membrane
Sits on connective tissue
What important structures in the heart are formed from the endocardium?
Valves
Describe the structure of the myocardium
Branching fibres of myocytes (cardiac muscle)
Striated, mononucleate muscle with lots of mitochondria and a rich capillary bed
Muscle bundles in different planes to close down chamber lumen
Intercalated discs connect individual cells:
- Gap junctions
- Desmosomes
Describe the structure of the epicardium
Simple squamous epithelium sitting on basement membrane, attached to connective tissue
Epithelium also known as visceral layer of the serous pericardium
Contains main branches of coronary arteries
May be fatty
The left border of the heart corresponds with which chamber?
Left ventricle
The right border of the heart corresponds with which chamber of the heart?
Right atrium
remember the hearts kinda tilted so that the right side faces down and out
What are the main abnormalities associated with the valves of the heart?
Incompetence = widening
Stenosis = narrowing
Aside from structural abnormalities, what else can happen to cause harm to the valves of the heart?
Bacterial endocarditis infection
What are the atrio-ventricular valves?
Mitral & tricuspid
What is the collective name for the aortic and pulmonary valves?
Semi-lunar valves
What is the cardiac skeleton?
Dense connective tissue thing that lies in the plane between the atria and ventricles
What is the function of the cardiac skeleton?
Structural support:
- Atrioventricular septum
- Roots of great vessels
- Anchorage for valves
- Myocytes/capillary network
Electrical insulation:
- Atria from ventricles
- Myocardium from great vessels
What are the coronary arteries?
Two arteries (left & right)
Located in epicardium
Supply the myocardium
Describe the blood flow through the coronary arteries and how this reaches the muscle tissue
At systole openings in aortic sinuses shielded by aortic valve cusps
At diastole elastic recoil of aorta closes aortic valve and blood enters arteries
At diastole myocardium relaxing and blood can flow into capillaries
What 4 things hold the heart in place?
- “Hangs” off great vessels
- Dense connective tissue bag
- Attachments
- Lined by serous pericardium
What is the heart ‘attached’ to?
Central tendon of diaphragm
Sternum
Roots of great vessels
The serous pericardium cells secrete a fluid that acts as a lubricant
What is this called and how does this benefit the function of the serous pericardium?
Pericardial fluid
Allows the heart to slip about during cardiac cycle
What 3 layers makes up the general structure of blood vessels?
Tunica adventitia (aka externa) - outermost
Tunica media
Tunica intima
What 3 layers make up the heart wall?
Epicardium
Myocardium
Endocardium
What makes up each layer of arteries?
Tunica adventitia:
- Fibrous connective tissue
Tunica media:
- Muscle
- Elastic tissue
Tunica intima:
- Epithelium + basement membrane
- Connective tissue
How is the heart wall different from blood vessels in terms of what makes up the layers?
Broadly similar
except the heart’s outer layer (epicardium) has an epithelial layer and basement membrane as well as connective tissue
What would you expect to find near a large artery?
An accompanying large vein
Generally, how is arterial structure different from venous structure?
Arteries smaller diameter than accompanying vein
Arteries thicker wall than accompanying vein
Arteries thicc media, thin adventitia
Veins thin media, thicc adventitia
Histologically, what appearance do veins often have?
Folded and floppy looking
Which type of blood vessel has the largest total surface area within the entire CVS?
Capillaries
What are the 2 types of arteries?
Give examples of each
Elastic - conducting arteries
- Aorta
- Common Carotid
- Pulmonary
Muscular - distributing
- Femoral
- Radial
- Coronary
Why are elastic arteries necessary?
Stretches with systole
Recoils during diastole to maintain high pressure
Maintains a high pressure, smooth blood flow
What causes elastic arteries to be elastic?
Lots of elastic fibres present in the Tunica media, and relatively little smooth muscle
Present in layers - laminae
Secreted by smooth muscle cells
What do elastic arteries look like histologically?
Elastic fibres = blue/purple coloured
Elastic arteries have large blue area (Tunica media) which muscular arteries lack
What do muscular arteries look like histologically?
Large tunica media - smooth muscle cells
Only elastic (blue) layers are present at the boundaries between the different tunica layers
- These are very thin though
- These layers are the Internal elastic lamina & Outer elastic lamina
Often, the tunica intima is bumpy looking at the edge
How does the structure of arterioles differ from that of arteries?
No Tunica adventitia
Tunica media made up of 1 or 2 layers of smooth muscle cells (but it is still the thickest part)
No IEL and i assume no OEL
Rich sympathetic nerve innervation
Histological images are much closer up than artery photos. This means the nuclei of cells are more obvious
How can arterioles have both local and systemic effects?
Can control blood flow to certain areas
Can also affect blood pressure (systemic)
- This is why blood pressure medication often targets smooth muscle receptors and makes them relax
Describe the structure of capillaries and how they differ from other blood vessels
Only made of Tunica intima
- Endothelial cell + basement membrane
Very thin
- 4-15µ average diameter
- 1 RBC thin
What type of cell allows capillaries to alter blood flow through them?
Pericytes - incomplete ring cells surrounding basement membrane that have contractile properties
What are the 3 types of capillaries?
Continuous
- complete basal lamina and complete endothelial coverage
Fenestrated
- A couple holes in the endothelial layer but a complete basal lamina
Discontinuous
- fuck ton of holes in the endothelial layer and in the basal lamina
Where are continuous capillaries found?
What are they good for?
Muscle, brain
Can control what leaves them, as they can only pass through the endothelial cells or through junctions
Great deal of control^
Describe the uses of fenestrated capillaries
Used in endocrine glands - eg. kidney renal corpuscle
Have pores up to 100µm in diameter that stuff goes through
Also MAY contain protein diaphragms which only let stuff with the correct charge or molecular weight through
What are the uses of discontinuous capillaries?
Liver, spleen, bone marrow
Free passage of fluid and cells out/in
What are sinusoids?
Type of discontinuous capillary
Larger diameter
Tunica intima contains phagocytic cells
Found where lots of exchange takes place - eg. liver, some endocrine glands
What allows the body to bypass capillary beds?
What is this called, and when is it used?
Precapillary SPHINCTAAA
These shut of capillaries and force blood to bypass them in a process called Arteriovenous shunts (AV shunts)
Useful in things like thermoregulation
Describe the layer structure of veins
T.intima is thin
IEL and OEL thin or absent
T.media v thin or absent
T adventitia - collagenous tissue with some Smooth M
T. intima folds to forms valves to prevent back-flow
Why are valves needed in veins but not in arteries?
Arteries are high pressure so there is no chance of backflow
Veins are low pressure
What is the difference between superficial and deep veins?
Superficial:
- Thick walled
- Not supported or near arteries
Deep:
- Thin walled
- Accompany arteries
- Surrounding support from deep fascia and muscles
Why is it incorrect to call it ‘lymphatic circulation’?
It is not a circulation
Lymphatic system is open ended - it’s like tree roots sticking into the ground, whereas the circulatory system is like train network
Where are lymph nodes commonly found?
found alongside major veins and around origins of major arteries
What feature do both veins and lymph vessels have?
Valves
Describe the main features of lymph vessels’ structure
Lined by very thin endothelium
No fenestrations
Absent / rudimentary basal lamina
Lumen maintained at –ve hydrostatic pressure
Anchoring filaments – fine collagenous filaments link endothelial cell to surrounding tissue keeping lumen open
No red blood cells in lumen
Valved
Why can some blood vessels be described as organs by themselves?
They have a nerve supply:
- Either just sympathetic (skin) or both parasymp. and symp.
They have a blood supply:
- Vasa vasorum
They have lymphatic drainage:
- Tunica adventitia has lymphatic drainage
What key feature can you use to differentiate blood vessels from nerves or lymph vessels?
Blood vessels = RBC’s will be visible
In what ways are capillaries specialised for exchange?
Lots of them
- every tissue within 100m of one
Thin-walled
- presents a small diffusion barrier
Small diameter
- big surface area:volume ratio
